5.7 The role of the lymphatic system

what is the lymphatic system?

The lymphatic system is a network of tubes (vessels) and organs that cleans your body's tissues by producing antibodies and lymphocytes to destroy pathogens

what is a cytotoxic T cell?

a white blood cell that destroys infected or cancerous cells by releasing a death ligand so that the cell can undergo apoptosis

what are antibodies?

Y shaped proteins created by plasma cells that attach to the foreign invaders and signal for help by attracting phagocytes

• contains two antigen biding sites and has the variable and constant region

what do naive b cells do?

from B lymphocytes they drive humoral immunity, which can then be activated to form plasma b cells and memory b cells

what do naive T cells do ?

from t lymphocytes they drive cell-mediated immunity without antibodies and can form naive T cells which bridge off to form naive helper T cells and naive cytotoxic T cells which further bridge off to mature cytotoxic T cells and memory T cells

why are helper T cells used in both humoral and cell-mediated immunity?

• helper T cells work in both as they release cytokines to allow for cell expansion and selection to occur in activated B,T and cytotoxic cells

what are the primary lymphatic organs or tissues?

• Bone marrow is the sponge middle part of the bone where immune cells are produced.

immune cells that remain in the bone marrow mature into B cells

• Thymus the immune cells that move from bone marrow to th thymus into T cells

what are the secondary lymphoid organs or tissues?

• lymph nodes collect and filter lymph fluid drained from the body as it travels along lymph vessels, trapping foreign materials anywhere lymphocytes can come across antigens and response to them (using inflamed lymph nodes)

• the spleen is a dark blood-filled organ that filters the blood, removes old red blood cells, detects foreign invaders and produces antibodies

what are the cells involved in the adaptive immune system?

• antigen presenting cells

• naive B and T cells

• activated B and T cells

• plasma B cells

• memory B and T cells

• cytotoxic T cells

• naive and activated cytotoxic T cells

what is self-tolerance?

the inability of an adaptive immune system to respond to the bodies own self antigens

what are lymph nodes?

Lymph nodes are the site of antigen recognition, in which T and B lymphocytes come into contact with their specific antigens. This results in clonal selection and expansion.

what are antigen-body complexes?

when an antibodies paratope matches perfectly with an antigens epitope

what does it mean if a cell has a letter next to it?

if it has the T or B with its name its a lymphocyte

What are antigen presenting cells?

once am APC such as a centric cell engulfs.a pathogen, it presents an antigen from this pathogen on the MHC - II markers on the outside of the outside of cell and moves to the lymph nodes to meet with helper T cells

what are helper T cells?

helper T cells are involved in kickstarting one of the two adaptive immune pathways

• cell-mediated and humoral

what are the two binding sites on antibodies which bind to specific foreign antigens in humoral immune response?

• constant region - the same in every antibody

• variable region - unique to a specific antigen and contains the antigen binding site

what are lymphocytes

(same as leukocytes/white blood cells) that is specific to adaptive immunity which detect invading pathogens and initiate an immune response

what are plasma b cells?

secretes large amounts of antibodies at a specific antigen. Contains lots of Golgi apparatus and rough endoplasmic reticulum to help with production.

what are memory b cells?

has receptors specific to a type of antigen and remembers it. When stimulated, it differentiates into plasma B cells and more memory B cells.

Long lived

what are memory T cells?

remembers a certain antigen to provide long-term immunity for future infections by that pathogen

what are B lymphocytes?

produced and matured in bone marrow and travels to the spleen and lymph nodes. It produces antibodies, which bind to a specific epitope on the surface of pathogens, labelling it for engulfment and destruction by macrophages.

Works in blood and lymph (extracellular pathogens - outside cells).

B cells are antigen presenting cells (APCs).

what are T lymphocytes?

produced in bone marrow and matures in the thymus. They don't have antibodies. Work within cells infected by pathogens (intracellular pathogens - within cells).